O2 sensor or catalytic converter

last week I had to have my coils and coil housing changed, after that the service engine light came on and when I am driving, or when I'm stopped, it does this little jump thing, almost like a hiccup or something. It reads the code PO 240 and says bank 1 is below threshold for the current engine operating condistions. From what I understand this means it needs a new O2 sensor or catalytic converter or both. Where are they at on the car? Is this something that can be done at home or do I need a mechanic to do it? I have a 2001 Pontiac Grand Am 2.4.

Thanks for your help!

Welcome to AF. O2 sensors are easily done, they basically look like spark plugs in your exhaust. You should have 2 of them, one before the converter and one either in the converter or right after the converter. You do need a special socket to get them out, most of the parts stores have them readily available. As for the converter, it's welded to the pipes on your car. Unless you know how to weld, have a shop do it for you.

Thank you for the advice. My husband is going to change the O2 sensors today, does he need to change both of them? Better question, if the cat. converter is bad and needs to be changed should the O2 sensors be changed too, or the other way around. Basically does he need to change both?
Also I've noticed if I turn the AC off the car won't do the "hiccup" as I call it, thing anymore, does that signal that it is a higher chance it could be the O2 sensor over the cat.?
Thanks for any help!